It has always been desirable to modify surface characteristics to achieve useful properties. In particular it is desired to be able to modify surface properties that are important in connection with antimicrobial and biocompatible objects. Examples of known surface modifications for different purposes are outlined below.
U.S. Pat. No. 6,224,983 discloses an article with an adhesive, antimicrobial and biocompatible coating comprising a layer of silver stabilised by exposure to one or more salts of one or more metals selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium and osmium. The thickness of the silver layer is in the range 2-2000 Å (Angstrom, Angstrom, 10−10 m) and further disclosed ranges are 2-350 Å and 2-50 Å. There are also examples of a thickness of the silver layer of 50 Å, 350 Å, 500 Å, and 1200 Å. The substrate may be latex, polystyrene, polyester, polyvinylchloride, polyurethane, ABS polymers, polycarbonate, polyamide, polytetrafluoroethylene, polyimide or synthetic rubber.
U.S. Pat. No. 5,965,204 discloses a method for preparing an article made of a nonconducting substrate having a coating comprising a silver layer, which has been deposited after activating the surface with stannous ions. There is also disclosed a coating further comprising a platinum group metal or gold. The thickness of the silver layer is in the range 2-2000 Å and further disclosed ranges are 2-350 Å and 2-50 Å. There are also examples of a thickness of the silver layer or 50 Å, 350 Å, 500 Å, and 1200 Å.
U.S. Pat. No. 5,747,178 discloses an article made by depositing a silver layer. The layer is said to be adhesive, antimicrobial and biocompatible. The silver layer may be stabilized by exposure to a salt solution of one or more platinum group metals or gold. The thickness of the silver layer is in the range 2-2000 Å and further disclosed ranges are 2-350 Å and 2-50 Å. There are also examples of a thickness of the silver layer of 50 Å, 350 Å, 500 Å, and 1200 Å. The article may be made of latex, polystyrene, polyester, polyvinylchloride, polyurethane, ABS polymers, polycarbonate, polyamide, polytetrafluoroethylene, polyimide or synthetic rubber.
U.S. Pat. No. 5,395,651 discloses a method of preparing an antimicrobial device comprising a nonconducting material with a silver coating. The coating also comprises a platinum group metal and/or gold. The method comprises the steps: 1 activating the surface to be coated, 2 depositing silver on the surface, 3 treating the surface with a salt of a platinum group metal and/or gold, which is to be carried out for only sufficient time to result in a thin coating 4 rinsing with water. The treatment of step 3 can utilise a salt of platinum or palladium in combination with gold. Nothing is said about the thickness of the coating of the platinum group metal and/or gold. The coating is only described as a thin coating. Nothing is said about metal particles on the silver coating. The thickness of the silver layer is in the range 2-2000 Å and further disclosed ranges are 2-350 Å and 2-50 Å. There are also examples of a thickness of the silver layer of 50 Å, 350 Å, 500 Å, and 1200 Å.
U.S. Pat. No. 5,320,905 discloses an adhesive, antimicrobial, and biocompatible coating consisting essentially of a layer of silver overlaid by one of more platinum group metals or gold. The coating may be transparent to the human eye. The thickness of the silver layer is in the range 2-2000 Å and further disclosed ranges are 2-350 Å and 2-50 Å. There are also examples of a thickness of the silver layer of 50 Å, 350 Å, 500 Å, and 1200 Å. The article may be made of latex, polystyrene, polyester, polyvinylchloride, polyurethane, ABS polymers, polycarbonate, polyamide, polytetrafluoroethylene, polyimide or synthetic rubber.
U.S. Pat. No. 5,695,857 discloses antimicrobial surfaces with several layers of one first metal and a second nobler metal. The antimicrobial active metal may for instance be platinum, gold, silver, zinc, tin, antimony and bismuth. The nobler metal may for instance be selected from the group consisting of platinum, osmium, iridium, palladium, gold, silver and carbon. The surface is to be used with biological fluids and each of the layers not in contact with the substrate are discontinuous so that the layer below is exposed. One example of a surface is silver coated with gold or platinum. Other examples are copper in combination with silver, copper in combination with a copper silver alloy, copper in combination with gold or a silver copper alloy in combination with gold.
CH 654 738 A5 discloses surgical implants made of stainless steel, which is coated with a first layer of copper and a second layer of silver, gold, rhodium or palladium. Silver is described to have a bactericidic action. CH 654 738 A5 explicitly discloses a surface where stainless steel is coated with 10 μm copper and 5 μm (50 000 Å) palladium. All surfaces disclosed in CH 654 738 A5 have a layer of  μm copper (100 000 Å) and either 10 μm silver or 5 μm gold or 5 μm palladium.
WO 2005/073289 discloses fibres made of a polymer composite comprising metal nanoparticles. It is stated that many metals have antimicrobial effects. Antimicrobial fibres are mentioned. One example is a hydrophilic fibre used in antimicrobial would dressings. Fibres with antimicrobial properties can comprise Ag, Au, Pt, Pd, Ir, Sn, Cu, Sb, Bi or Zn or any combination thereof.